Modern optical sensors and other electronic devices are often mounted within gimbal mechanisms to achieve free movement in multiple axes, which is especially true for many military applications. However, modern electronic devices often require hundreds or even thousands of signals to function properly, and each of these cables must be arranged in a manner that allows repeated motion in each gimbal axis without cable damage.
Further complicating this arrangement, any cross-axis cable management system must be compatible with a high number of both conventional cables and more sensitive, fiber-optic ribbon cables. Finally, friction or drag must be minimized or the additional friction leads to increased torque requirements, necessitating larger, heavier, more powerful motors.
Traditional methods of managing cables across rotational axis include slip rings and twist capsules. Slip ring is a type of electrical swivel and enables rotational motion of the cable without physically twisting the cable.
Slip rings are subject to wear due to electrical arcing, and also from being in physical contact with the rotating surfaces. Also slip rings are not suitable for transmitting high speed data nor in combustible environments due to electrical arcing. A major limiting factor to the maximum transmission rate while transmitting high frequency signals through slip rings is distortion of the waveforms due to reflections from impendence discontinuities. Impedance discontinuities can occur throughout the slip ring wherever different forms of transmissions lines interconnect and have different surge impedances.
The loss of energy through slip rings increases with frequency due to a variety of effects, such as multiple reflections from impedance mismatches, circuit resonance, distributed inductance and capacitance, dielectric losses and skin effect. Hence usage of slip rings for cable management generally limited to conventional cables and not suitable for use with fiber optic cables.
Fiber optic cables require minimum bend radii to operate within required performance specifications. The minimum bend radius of a fiber optic cable depends upon a variety of factors, including the signal handled by the fiber optic cable, the style of the fiber optic cable, and equipment to which the fiber optic cable is connected. Specialized rotational joints for fiber optic cable management have been developed for use with a gimbal, but most such joints enable the use of only a single multi mode fiber, and none can manage the high number of single mode fibers or fiber ribbons required to operate modern high resolution imaging systems.
A need therefore exists for a cable management system capable of routing large numbers of conventional and fiber optic or fiber optic ribbon cables across multiple gimbal axes without loss of performance or cable damage.